[CodeComplete] Constructor overload candidates report as vector(int) instead of vector<string>(int)

[sammccall]

Summary

This is shorter, shouldn't be confusing (is consistent with how they're declared),
and avoids messy cases that are printed as myclass<type-param-0-0>(int) in the
case of partial specialization.

Fixes part of https://github.com/clangd/clangd/issues/76

[merge_guards_bot]

Build result: pass - 60091 tests passed, 0 failed and 729 were skipped.
Log files: console-log.txt, CMakeCache.txt

[hokein]

clang/test/CodeCompletion/templates.cpp

35

shouldn't be now X<T *> after your recent patch?

[sammccall]

clang/test/CodeCompletion/templates.cpp

35

Sadly not, that patch doesn't fix every case (and I couldn't work out how to fix most of them)

clang/lib/Sema/SemaCodeComplete.cpp

static void AddOverloadParameterChunks(ASTContext &Context,
   }
 }
 
 CodeCompletionString *
 CodeCompleteConsumer::OverloadCandidate::CreateSignatureString(
     unsigned CurrentArg, Sema &S, CodeCompletionAllocator &Allocator,
     CodeCompletionTUInfo &CCTUInfo, bool IncludeBriefComments) const {
   PrintingPolicy Policy = getCompletionPrintingPolicy(S);
+  // Show signatures of constructors as they are declared:
+  //   vector(int n) rather than vector<string>(int n)
+  // This is less noisy without being less clear, and avoids tricky cases.
+  Policy.SuppressTemplateArgsInCXXConstructors = true;
 
   // FIXME: Set priority, availability appropriately.
   CodeCompletionBuilder Result(Allocator, CCTUInfo, 1,
                                CXAvailability_Available);
   FunctionDecl *FDecl = getFunction();
   const FunctionProtoType *Proto =
       dyn_cast<FunctionProtoType>(getFunctionType());
   if (!FDecl && !Proto) {

clang/test/CodeCompletion/templates.cpp

void f() {
   v.foo();
   // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:18:8 %s -o - | FileCheck -check-prefix=CHECK-CC1 %s
   // CHECK-CC1: allocator<<#typename T#>>
   // CHECK-CC1-NEXT: vector<<#typename T#>{#, <#typename Alloc#>#}>
   // RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:19:5 %s -o - | FileCheck -check-prefix=CHECK-CC2 %s
   // CHECK-CC2: foo
   // CHECK-CC2: in_base
   // CHECK-CC2: stop
-  
+}
 
+template <typename> struct X;
+template <typename T> struct X<T*> { X(double); };
+X<int*> x(42);
+// RUN: %clang_cc1 -fsyntax-only -code-completion-at=%s:32:11 %s -o - | FileCheck -check-prefix=CHECK-CONSTRUCTOR %s
+// CHECK-CONSTRUCTOR: OVERLOAD: X(<#double#>)
+// (rather than X<type-parameter-0-0 *>(<#double#>)